A variation of the Dutch oven. It is the act of letting a silent fart when in bed with your wife or girlfriend, then slowly lifting your leg beneath the sheets (forming the "tunnel"), and then let your leg down, allowing the weight of the covers to gently waft the stench of your fart into the face of your significant other.

My wife is always complaining that I'm not romantic enough, so last night I gave her a Tunnel of Love.